1. Field of the Invention
The present invention relates to a printing apparatus that can accept a plurality of jobs. In addition, the invention further relates to a method for controlling such a printing apparatus, a program, and a storage medium.
2. Description of the Related Art
Some printing apparatuses have an auto cassette change (ACC) function. After a paper-feeding unit that is being used for printing has run out of sheets of paper having a size required for printing, a known printing apparatus having the ACC function automatically searches for a substitute paper-feeding unit with sheets of paper having the same size as that of the sheets of paper set in the paper-feeding unit that has run out. The ACC function enables such a printing apparatus to continue printing by feeding the sheets of paper set in the substituted paper-feeding unit. Therefore, it is possible to continue printing when the paper-feeding unit that is currently being used for printing has run out of sheets without any need for a user to give manual instructions for performing a paper-feeding unit switchover.
When such an ACC function is used, however, it is only after the paper-feeding unit that is currently being used for printing has run out of sheets that the printing apparatus starts an automatic search for a substitute paper-feeding unit that can take over the job. Upon finding the substitute paper-feeding unit, the paper-feeding source is switched over from the paper-feeding unit that has run out of the sheets to the substitute paper-feeding unit. Then, print operations are resumed by feeding sheets from the substitute paper-feeding unit. When such cassette change processing is performed, it is impossible to feed any sheet of paper from a point in time at which it was detected that the paper-feeding unit had run out of sheets to a point in time at which the feeding of sheets is resumed. Therefore, print operations have to be paused during such a time period, which results in downtime.
As a technique for improving the ACC function, a method for continuing printing with the use of sheets set in a substitute paper-feeding unit without waiting for the running out of sheets of paper having a size required for printing at the paper-feeding unit that is currently being used for printing has been proposed in the technical field to which the present invention pertains (Japanese Patent Laid-Open No. 2008-030451). In such an improved ACC method, when it is detected that the amount of sheets remaining in a paper-feeding unit that is currently being used for print processing has reached a predetermined amount, a substitute paper-feeding unit in which sheets having the same size as that of the sheets set in the currently-used paper-feeding unit are set is searched for while continuing the print processing with the use of sheets remaining in the currently-used paper-feeding unit. Then, upon the finding of the substitute paper-feeding unit, the printing apparatus performs control so that paper should be fed from the found substitute paper-feeding unit. Therefore, it is possible to decrease the possibility that paper-feeding operation is paused, which results in reduction in downtime.
Another known printing apparatus can output printed sheets with sheets of index paper being inserted at arbitrary page positions in a stack of outputted sheets. Prior to such index insertion, sets of sheets of index paper each made up of more than one sheet have been provided in a paper-feeding unit of the printing apparatus. Such a printing apparatus makes it possible for a user to easily identify each section in the text of the printed sheets while using each index sheet inserted as a mark.
However, when sheets of print-processing target medium each set of which is made up of more than one sheet are set in a paper-feeding unit, in some cases, it is not possible to obtain a correct output if the paper-feeding units are switched from the current one to another upon detecting that the remaining amount of sheets set therein has reached a predetermined amount.
For example, it is assumed herein that printing is performed under a job instruction that five index sheets should be inserted in each print copy, that is, in each one set of sheets that are to be outputted for the job. If a paper-feeding source is switched from the paper-feeding unit that is currently being used for feeding index paper to a substitute paper-feeding unit at a point in time at which only three of five index sheets have been inserted, which means that two index sheets have not been inserted yet, upon detecting that the remaining amount of sheets set in the currently-used paper-feeding unit has reached the predetermined amount, index sheets will not be inserted correctly in the print output.
However, if it is controlled so that a paper-feeding unit switchover should be performed only after the index paper-feeding unit that is currently being used for the feeding of index paper has run out of index sheets, print operations have to be paused due to a failure in the feeding of index paper that occurs as a result of the running-out of index sheets set in the currently-used paper-feeding unit, which results in downtime.